Television Technology

television (TV), the electronic delivery of moving images and sound from a source to a receiver. By extending the senses of vision and hearing beyond the limits of physical distance, television has had a considerable influence on society. Conceived in the early 20th century as a possible medium for education and interpersonal communication, it became by mid-century a vibrant broadcast medium, using the model of broadcast radio to bring news and entertainment to people all over the world. Television is now delivered in a variety of ways: “over the air” by terrestrial radio waves (traditional broadcast TV); along coaxial cables (cable TV); reflected off of satellites held in geostationary Earth orbit (direct broadcast satellite, or DBS, TV); streamed through the Internet; and recorded optically on digital video discs (DVDs) and Blu-ray discs.

The technical standards for modern television, both monochrome (black-and-white) and colour, were first established in the middle of the 20th century. Improvements have been made continuously since that time, and television technology changed considerably in the early 21st century. Much attention was focused on increasing the picture resolution (high-definition television [HDTV]) and on changing the dimensions of the television receiver to show wide-screen pictures. In addition, the transmission of digitally encoded television signals was instituted to provide interactive service and to broadcast multiple programs in the channel space previously occupied by one program.

Despite this continuous technical evolution, modern television is best understood first by learning the history and principles of monochrome television and then by extending that learning to colour. The emphasis of this article, therefore, is on first principles and major developments—basic knowledge that is needed to understand and appreciate future technological developments and enhancements.